1085z HD video limits

I just bought an 8 gig SD card mistakenly thinking I could increase the HD video capability of my 1085z to greater than 29 minutes. I have now learned that is not possible.

I'm not sure I fully understand why it is limited to 29 minutes. With that said, this may be a stupid question so bear with me.

How/when does the camera "reset" the 29 minute limit? Example - I take a few videos and use up the 29 minute limit. Does it "reset" when these videos are transferred off the SD card? When the card is removed? When I take the batteries out? What am I missing in this concept?